Interpretive Summary: There are numerous methods available for measuring reducing sugars (mostly glucose and fructose simple sugars) in molasses samples, with titration methods preferred for molasses trade. An international research study was undertaken to compare the accuracy and precision of the different methods. Molasses samples included those from sugarbeet and sugarcane factories, and sugarcane refineries. Precision was best in the titration methods. A new, international enzymatic method gave quite accurate results and warrants further investigation.

Technical Abstract:
With more processing of sugarcane or sugarbeet for fuel alcohol production, there is an increasing emphasis on the minimizing of losses from fermentable reducing sugars to improve alcohol yields. Consequently, methods to measure reducing sugars in molasses and other sugar products have become more important. Reducing sugars in six molasses samples from the USA, UK, Turkey, South Africa and Brazil were measured using copper reduction (Luff Schoorl and Lane & Eynon), chromatographic (High Performance Liquid Chromatography HPLC and Ion Chromatography IC), and enzymatic ICUMSA (International Commission for Uniform Methods in Sugar Analysis) methods. The final molasses samples included two beet molasses, two sugarcane factory molasses, and two sugarcane refinery molasses. Precision and mean results were compared. The Lane & Eynon method had consistently the best precision. Precison was worst in the enzymatic and chromatographic methods than both copper reduction methods and followed the order: Lane & Eynon>Luff Schoorl>HPLC=IC>Enzymatic. Lane & Eynon, and particularly Luff Schoorl, methods significantly (P<0.01) and consistently over-estimated “apparent sucrose” in molasses, as compared to the more accurate chromatographic results, because they measure all reducing substances present. HPLC generally gave slightly, but significantly, higher mean results than IC. The new ICUMSA enzymatic method (Draft Method No. 8) correlated well with both copper reduction and chromatographic methods, but tended to under-estimate apparent sucrose. However, enzymatic results were close (not significantly different) to IC results, suggesting that the enzymatic method could be more accurate than copper reduction methods and, therefore, warrants further investigation.